The best course of action is to just go along with it while you get legal council. The more information you can glean while you're working there will only help

The best course of action is to just go along with it while you get legal council. The more information you can glean while you're working there will only help strengthen your case. If you simply lawyer up and confront the owners, they'll go into bunker mode, fire you and then lawyer up themselves. Act normal, and continue to work and essentially collect as much as evidence you can. You can drop hints, talk to people to find out what they know, etc. The more you know, you can start to build a timeline and the implications that the company was effectively doing this behind your back for nefarious reasons. The more you have documented, the more you strengthen your case so when its time to actually threaten them with legal recourse, you'll have all the evidence you need while they'll be scrambling to build a defense. Hope this turns out well for you!